....Is it to avoid any confusion as to whether or not the item is still available for purchase? If so, there's a simple code you can use for "strikethrough" text (example: strikethrough). Just use < s > and < / s > (without spaces) in the same way you'd use < b > and < / b > for creating boldface type.

Anyway, the Mystery of the Disappearing Prices has always puzzled me, but perhaps some sellers have their reasons for deleting their prices so quickly. I dunno...